JavaWeb 文件上传

最新推荐文章于 2022-08-16 18:03:36 发布

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最新推荐文章于 2022-08-16 18:03:36 发布

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文章标签： javaweb

本文链接：https://blog.youkuaiyun.com/m0_51517626/article/details/122497438

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文件上传

不论是文件的上传还是下载都是网页中很常见的功能。

步骤

必须要有 form 标签，发送方式必须为 post
form 标签的 encType 属性值必须为 multipart/form-data
from标签中须使用 input type=file
需要编写服务器来接收文件

请求说明：

请添加图片描述

实现文件上传

jsp

<body>
<form action="http://localhost:8080/WebTest06_upload_download/uploadServlet" method="post" enctype="multipart/form-data" >
    昵称:<input type="text" name="nickname"><br/>
    头像:<input type="file" name="icon"><br/>
    <input type="submit" value="上传头像">
</form>
</body>

引入commons-fileupload用于文件上传与下载

maven导包

<!-- https://mvnrepository.com/artifact/commons-fileupload/commons-fileupload -->
<dependency>
  <groupId>commons-fileupload</groupId>
  <artifactId>commons-fileupload</artifactId>
  <version>1.3.1</version>
</dependency>

使用其中的ServletFileUpload完成文件上传与下载

ServletFileUpload类介绍

public class ServletFileUpload extends FileUpload {
    private static final String POST_METHOD = "POST";

    //是否为多段数据
    public static final boolean isMultipartContent(HttpServletRequest request) {
        return !"POST".equalsIgnoreCase(request.getMethod()) ? false : FileUploadBase.isMultipartContent(new ServletRequestContext(request));
    }

    public ServletFileUpload() {
    }

    public ServletFileUpload(FileItemFactory fileItemFactory) {
        super(fileItemFactory);
    }

    //解析请求放入list中
    public List<FileItem> parseRequest(HttpServletRequest request) throws FileUploadException {
        return this.parseRequest(new ServletRequestContext(request));
    }

    //解析请求放入map中
    public Map<String, List<FileItem>> parseParameterMap(HttpServletRequest request) throws FileUploadException {
        return this.parseParameterMap(new ServletRequestContext(request));
    }

    public FileItemIterator getItemIterator(HttpServletRequest request) throws FileUploadException, IOException {
        return super.getItemIterator(new ServletRequestContext(request));
    }
}

实现服务器端代码（servlet）

/**
 * @describe: 文件上传Servlet
 * @author: ylt
 * @create: 2022-01-13 21:24
 **/

public class UploadServlet extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("文件上传了");


        //创建FileItemFactory实现类对象
        FileItemFactory fileItemFactory = new DiskFileItemFactory();
        //创建ServletFileUpload对象用于文件的上传和下载
        ServletFileUpload servletFileUpload = new ServletFileUpload(fileItemFactory);

        //判断请求是否为多段请求，只有请求是多段的才是文件上传请求
        if (ServletFileUpload.isMultipartContent(req)){
            //解析+处理
            try {
                List<FileItem> fileItems = servletFileUpload.parseRequest(req);
                //遍历
                for (FileItem fileItem : fileItems) {
                    //如果是普通表单项
                    if (fileItem.isFormField()) {
                        System.out.println(fileItem.getFieldName() + ":" + fileItem.getString());
                    }else {
                        //如果是需要上传的文件
                        String name = new String(fileItem.getName().getBytes(),"UTF-8");
                        System.out.println("上传的文件名：" + name);
                        System.out.println("表单的name：" + fileItem.getFieldName());
                        //写入
                        fileItem.write(new File("F:\\Java_Study\\JavaWeb_Study\\WebTest06_upload_download\\src\\main\\icon\\"+name));
                    }
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}
   }
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}